The invention relates to seats for transport vehicles, in particular for automobiles having a seat whose back has a first cross joint for adjusting the seatback tilt to achieve the positioning desired by the occupant.
A second joint, generally located above a first joint enables the seatback to be folded down to an essentially horizontal position, whereby it forms a tabletop. This position, which can be used to support various objects, reduces the volume of the seat when it is retracted inside the vehicle, and increases the interior volume of the vehicle when the seat is removed from the vehicle.
In most current seats, each joint is associated with its own locking means. For example, a seat having a toothed segment cooperating with toothed locking plates, provides each with its own control means. As a result, one can confuse the control means when trying to manipulate the seat to various positions. One may, for example, inadvertently unlock the second fold-down joint while trying to adjust the seatback position for comfort.
Additionally, seats equipped with seatbelt anchoring points may hurl occupants forward with no restraint, if adjustments are attempted while the vehicle is being sharply braked. This may result in injury, or worse, to an occupant.
To remedy these situations, seats with double-jointed backs have been equipped with a single control that unlocks both seatback joints and cooperates with additional means to unlock the second fold-down joint only when the seatback is in a given position, by rotating around the first comfort-adjustment joint.
Current devices of this type are cumbersome and have locking means that are subjected to additional force components, requiring that they be oversized, which increases the total weight of the seat. The large size makes it difficult to upholster the seatback, which must have local recesses for the control mechanism and means. Hence predecessor configurations make the seats and their control mechanisms more expensive, more fragile, and more difficult to install.
The goal of the invention is to overcome these drawbacks by providing a device of reduced size for adjusting a double-jointed seatback using a single control, thereby enabling the area and weight of the device to be reduced as well as reducing the reaction stresses on the locking plates.
The device according to the invention, provides a seat pan structure joined on at least one side to a convex toothed sector that is centered on a first joint. The first joint passes through the seat pan structure and pivots relative to a two-part housing extending on each side of the toothed sector. The seatback structure is joined on at least the same side as the seat pan structure to two arms that extend on either side of the housing. The arms are articulated on a second joint mounted on the housing. The seatback is also joined to a concave toothed sector centered on the second joint. The housing contains:
an upper locking plate able to mesh with the teeth of the concave toothed sector connected with the seatback; and
a lower locking plate able to mesh with the teeth of the convex toothed sector connected to the seat pan.
Between these two locking plates, a double pivoting cam secured to a transverse shaft parallel to the second joint and connected to a single control means, occupies a locking position by resting its opposed supports on ramp surfaces of each of the toothed locking plates thereby locking the two joints in place. An unlocking position relieves the supports from the ramp surfaces thereby releasing the locking plates and allowing them to move away from the corresponding toothed sectors.
Because of this arrangement, the locking means of concave and the convex toothed sectors are substantially aligned with the axis of rotation of the first joint. This eliminates reaction stress components in the event of an overload, and enables the size and weight of the seat to be reduced. Moreover, the arrangement of most of the elements in the housing engage between the two arms joined to the seat pan structure, which allows the device to be smaller, and facilitates its integration into the side of the seatback. This enables upholstering to be simpler to manufacture and install for the seatback.
In one embodiment, the upper toothed locking plate is joined to a stop arm extending in the housing towards a semicircular stop provided on the lower convex toothed sector to resist the unlocking of the locking plate except when the seatback is in the maximally advanced position by rotating around the first comfort adjustment joint.
Other features and advantages will emerge from the description that follows with reference to the schematic diagrams attached showing two embodiments of the device as examples.